Magnetic Sensor and Manfacturing Method Therefor

ABSTRACT

A magnetic sensor for detecting the intensity of a magnetic field in three axial directions, in which a plurality of giant magnetoresistive elements are formed on a single semiconductor substrate. A thick film is formed on the semiconductor substrate; giant magnetoresistive elements forming X-axis and Y-axis sensors are formed on a planar surface thereof; and giant magnetoresistive elements forming a Z-axis sensor are formed using slopes of channels in the thick film. Each of the slopes of the channels can be constituted of a first slope and a second slope, so that a magneto-sensitive element is formed on the second slope having a larger inclination angle. In order to optimize the slope shape and inclination with respect to each channel, it is possible to form a dummy slope that does not directly relate to the formation of the giant magnetoresistive elements.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of application Ser. No.10/584,666, filed May 29, 2007, the entire contents of which isincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to magnetic sensors and manufacturingmethods therefor, and in particularly to small-size magnetic sensors andmanufacturing methods therefor, in which three or more giantmagnetoresistive elements are arranged on a single substrate so as todetect the intensity of a magnetic field in three axial directions.

The present application claims priority on seven Japanese patentapplications, i.e., Patent Application No. 2005-77010 (filing date: Mar.17, 2005), Patent Application No. 2005-91616 (filing date: Mar. 28,2005), Patent Application No. 2005-88828 (filing date: Mar. 25, 2005),Patent Application No. 2005-131857 (filing date: Apr. 28, 2005), PatentApplication No. 2005-350487 (filing date: Dec. 5, 2005), PatentApplication No. 2005-91617 (filing date: Mar. 28, 2005), and PatentApplication No. 2005-98498 (filing date: Mar. 30, 2005), the contents ofwhich are incorporated herein by reference.

BACKGROUND ART

Conventionally, a variety of magnetic sensors have been developed. Forexample, Japanese Unexamined Patent Application Publication No.2004-6752 discloses a magnetic sensor in which three or more giantmagnetoresistive elements are arranged on a single substrate so as todetect the intensity of a magnetic field in three axial directions.

The magnetic sensor disclosed in the aforementioned paper is designedsuch that channels are formed on a silicon substrate, Z-axis giantmagnetoresistive elements are arranged on slopes of channels, and X-axisgiant magnetoresistive elements and Y-axis giant magnetoresistiveelements are arranged on a planar surface of the silicon substrate, thusreducing the overall size thereof.

In addition, a three-axial magnetic sensor, in which elongatedprojections composed of silicon oxide are formed, Z-axis giantmagnetoresistive elements are arranged on slopes of the elongatedprojections, and X-axis giant magnetoresistive elements and Y-axis giantmagnetoresistive elements are arranged on a planar surface of thesilicon substrate, is known.

-   Patent document 1: Japanese Unexamined Patent Application    Publication No. 2004-6752.

Problems to be Solved by the Invention

It is an object of the present invention to further reduce the overallsize and to improve the detection accuracy in a magnetic sensor in whichthree or more giant magnetoresistive elements are arranged on a singlesubstrate so as to detect the intensity of a magnetic field in threeaxial directions.

Means for Solving the Problems

In a first aspect of the present invention, a magnetic sensor is formedin such a way that a thick film formed on a semiconductor substrate issubjected to treatment so as to form a plurality of channels inparallel; Z-axis sensors are realized by a plurality of giantmagnetoresistive elements, which are constituted using magneto-sensitiveelements formed on slopes of channels and bias magnets for electricallyconnecting magneto-sensitive elements in series; and X-axis sensors andY-axis sensors are realized by a plurality of giant magnetoresistiveelements, which are arranged at prescribed positions on a planar surfaceof the thick film.

According to a manufacturing method of the aforementioned magneticsensor, a planation layer realizing planation by covering a wiring layerof a semiconductor substrate is formed; a passivation film is formed onthe planation layer; a thick film is formed on the passivation film; aresist film is formed on the thick film; the resist layer is partiallyremoved; the resist layer is subjected to heat treatment so as to makeside surfaces thereof slope; the resist film and thick film aresubjected to etching with an etching selection ratio of 1:1 so as toform a plurality of channels in the thick film; bias magnets forminggiant magnetoresistive elements are formed on a planar surface of thethick film as well as slopes, top portions, and bottom portions ofchannels; a giant magnetoresistive element film is formed; thesemiconductor substrate in which the giant magnetoresistive element filmis formed is arranged in proximity to a magnet array and is thensubjected to heat treatment; the giant magnetoresistive element film ispartially removed by etching; magneto-sensitive elements forming giantmagnetoresistive elements are formed on the planar surface of the thickfilm and the slopes of the channels; and a protection film is formed.

In the above, the passivation film can be constituted by an upper layerand a lower layer. In this case, the planation layer is partiallyremoved so as to make vias and pads be exposed; the upper layer of thepassivation film is removed from the vias and pads; the resist film issubjected to etching, and then the thick film remaining in the center ofthe vias as well as the lower layer of the passivation film are removedso as to make conductive portions of the vias be exposed; after theformation of bias magnets, a wiring film connecting between the biasmagnets and the conductive portions of the vias is formed; and after theformation of the protection film, the thick film covering the pads andthe lower layer of the passivation film are removed so as to make theconductive portions of the pads be exposed.

In a second aspect of the present invention, a plurality of channels areformed in the resist film before the formation of a plurality ofchannels in the thick film. That is, after the formation of the resistfilm, a mold having a plurality of projections corresponding to aplurality of channels formed in the thick film is pressed against theresist film so as to form a plurality of channels therein.Alternatively, after the formation of the resist film, a photomaskhaving a fine pattern, in which the number of channels per unit area isgradually increased from the center to both ends of the thick film, isarranged opposite to the resist film, which is then subjected toexposure and development, thus forming channels in the resist film.

In a third aspect of the present invention, after the heat treatment ofthe resist film, reactive ion etching is performed under high ionetching conditions on the resist film and thick film, thus forming aplurality of channels in the thick film. Alternatively, an insulatingfilm is formed using deposition of silicon oxide on the thick film byway of the high-density plasma CVD method; a plurality of projectionshaving linear ridgelines are formed at prescribed parts of theinsulating film; then, the insulating film having a plurality ofprojections and the thick film are subjected to etching under high ionetching conditions, thus forming a plurality of channels in the thickfilm, whereby the thick film remaining in vias and pads is reduced inthickness.

Thus, it is possible to form a plurality of channels connected in azigzag manner in the thick film; and it is possible to improve theplanation with respect to each of slopes of channels.

In a fourth aspect of the present invention, a prescribed inclinationangle is applied to each of slopes of channels by easy etching control;hence, it is possible to form giant magnetoresistive elements havinggood characteristics.

That is, an etching stopper film is formed between the thick film andthe semiconductor substrate in the magnetic sensor. Specifically, aninsulating film is formed between the thick film and the passivationfilm and is used as an etching stopper in execution of etching.

Thus, it is possible to increase the etching selection ratio between theresist film and the thick film. In addition, it is possible to make thethick film dent towards the etching stopper film, thus forming channelsby way of etching.

In a fifth aspect of the present invention, it is possible to improve asensing accuracy of a magnetic sensor due to variations of inclinationangles of slopes of channels formed in the thick film, in particular dueto variations of inclination angles between upper portions and lowerportions of slopes. That is, each of slopes of channels is formed by anupper-side first slope and a lower-side second slope, wherein the secondslope is greater than the first slope in terms of the inclination angle,and magneto-sensitive elements of giant magnetoresistive elements areformed on the second slope. Thus, it is possible to improve theplanation with respect to the surfaces of the magneto-sensitiveelements; hence, sensing directions of giant magnetoresistive elementsare adjusted in the Z-axis direction; and it is therefore possible torealize a magnetic sensor having a high sensitivity.

In a sixth aspect of the present invention, giant magnetoresistiveelements are formed selectively on the channels having prescribedshapes. Because, the peripheral shapes of the channels become uncertaindue to the difficulty of uniformly executing plasma etching, and thismakes it difficult to realize the desired planation and inclinationangle with respect to the peripheral portions and center portions of thechannels.

That is, a first dummy slope is formed in at least one of the channels;and no giant magnetoresistive element is formed on the first dummyslope. In addition, a second dummy slope is formed in proximity to theterminal end of the channels in longitudinal directions.

In a seventh aspect of the present invention, the terminal ends of theslopes of the channels formed in the thick film on the semiconductorsubstrate are rounded so as to realize uniformity in the slope shape andinclination angle.

Effect of the Invention

In the present invention, giant magnetoresistive elements for detectingthe intensity of a magnetic field in X-axis, Y-axis, and Z-axisdirections are mounted on a single semiconductor substrate, thusrealizing a small-size three-axial magnetic sensor. It is possible torealize a magnetic sensor having good performance because the thick filmformed on the semiconductor substrate is subjected to treatment so as toform channels, and magneto-sensitive elements of giant magnetoresistiveelements are selectively formed on slopes of channels having goodplanation. A giant magnetoresistive element film is deposited on wiringcomposed of a magnet film with respect to a recessed end of a via;hence, it is possible to avoid the occurrence of breakdown of wiring atcorners of a step portion. In addition, it is possible to realize giantmagnetoresistive elements having high stability against a magneticfield.

According to the manufacturing method of the aforementioned magneticsensor, it is possible to form channels and to form giantmagnetoresistive elements on slopes of the channels by way of a seriesof processes. Furthermore, it is possible to form vias and pads by wayof a series of processes. Thus, it is possible to efficiently produce amagnetic sensor.

A plurality of channels are formed in advance in the resist film on thesemiconductor substrate. This makes it possible to easily form channelshaving prescribed shapes in the thick film by way of etching; and it ispossible to improve the planation with respect to the slopes of thechannels. Thus, it is possible to form a Z-axis sensor having aprescribed sensing direction and a good sensitivity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A plan view showing giant magnetoresistive elements forming anX-axis sensor, a Y-axis sensor, and a Z-axis sensor arranged on asemiconductor substrate of a magnetic sensor in accordance with a firstembodiment of the present invention.

FIG. 2 A plan view showing an example of the internal structure of agiant magnetoresistive element.

FIG. 3 A plan view showing the structure of giant magnetoresistiveelements forming the Z-axis sensor.

FIG. 4 A cross-sectional view showing a method of forming giantmagnetoresistive elements forming the Z-axis sensor.

FIG. 5 A perspective view showing an example of the layout of giantmagnetoresistive elements forming the Z-axis sensor.

FIG. 6 A perspective view showing another example of the layout of giantmagnetoresistive elements forming the Z-axis sensor.

FIG. 7 Line-connection diagrams showing line connections between giantmagnetoresistive elements with respect to the X-axis sensor, Y-axissensor, and Z-axis sensor.

FIG. 8 A cross-sectional view showing the structure of a via in themagnetic sensor of the first embodiment.

FIG. 9 Cross-sectional views showing a manufacturing method of themagnetic sensor of the first embodiment.

FIG. 10 Cross-sectional views showing the manufacturing method of themagnetic sensor of the first embodiment subsequently to FIG. 9.

FIG. 11 Cross-sectional views showing the manufacturing method of themagnetic sensor of the first embodiment subsequently to FIG. 10.

FIG. 12 Cross-sectional views showing the manufacturing method of themagnetic sensor of the first embodiment subsequently to FIG. 11.

FIG. 13 A plan view and cross-sectional views showing the relationshipsbetween giant magnetoresistive elements and polarities of magnets of amagnet array used in a pinning process in the manufacturing method ofthe magnetic sensor of the first embodiment.

FIG. 14 A cross-sectional view showing the direction of a line ofmagnetic force exerted on giant magnetoresistive elements in the pinningprocess shown in FIG. 13( b).

FIG. 15 A plan view showing the structure of giant magnetoresistiveelements forming a Z-axis sensor in accordance with a second embodiment.

FIG. 16 A cross-sectional view showing a method of forming giantmagnetoresistive elements forming the Z-axis sensor shown in FIG. 15.

FIG. 17 Cross-sectional views showing a manufacturing method of amagnetic sensor in accordance with the second embodiment, whichcorrespond to FIG. 10 used in the first embodiment.

FIG. 18 Cross-sectional views showing processes for forming projectionsand channels in a zigzag manner in a channel forming region by way of astamper method shown in FIG. 17( c).

FIG. 19 Cross-sectional views showing the manufacturing method of themagnetic sensor of the second embodiment subsequently to FIG. 17.

FIG. 20 Cross-sectional views showing the manufacturing method of themagnetic sensor of the second embodiment subsequently to FIG. 19.

FIG. 21 A conceptual drawing showing a photomask having numerous finepatterns used for the formation of channels in a resist film on asemiconductor substrate, and a graph showing a pattern ratio.

FIG. 22 A graph showing the relationship between the pattern ratio andthe resist thickness after exposure.

FIG. 23 A cross-sectional view diagrammatically showing the shape of achannel formed using the photomask.

FIG. 24 Cross-sectional views showing a method of forming a plurality ofprojections having slopes in an insulating film of a channel formingregion by way of the high-density plasma CVD method in accordance with athird embodiment of the present invention.

FIG. 25 A cross-sectional view showing a method of forming giantmagnetoresistive elements forming a Z-axis sensor in accordance with afourth embodiment of the present invention.

FIG. 26 Cross-sectional views showing a manufacturing method of amagnetic sensor in accordance with the fourth embodiment of the presentinvention, which show processes to be performed subsequently to FIG. 9.

FIG. 27 Cross-sectional views showing the manufacturing method of themagnetic sensor of the fourth embodiment subsequently to FIG. 26.

FIG. 28 Cross-sectional views showing the manufacturing method of themagnetic sensor of the fourth embodiment subsequently to FIG. 27.

FIG. 29 Cross-sectional views showing the manufacturing method of themagnetic sensor of the fourth embodiment subsequently to FIG. 28.

FIG. 30 Cross-sectional views showing the manufacturing method of themagnetic sensor of the fourth embodiment subsequently to FIG. 29.

FIG. 31 A plan view showing giant magnetoresistive elements forming aZ-axis sensor mounted on a magnetic sensor in accordance with a fifthembodiment of the present invention.

FIG. 32 A cross-sectional view taken along line IV-IV in FIG. 31.

FIG. 33 An enlarged cross-sectional view of an area encompassed bydotted lines in FIG. 32.

FIG. 34 Cross-sectional views showing a manufacturing method of amagnetic sensor of a fifth embodiment, which is performed subsequentlyto FIG. 10.

FIG. 35 Cross-sectional views showing the manufacturing method of themagnetic sensor of the fifth embodiment subsequently to FIG. 34.

FIG. 36 A plan view showing giant magnetoresistive elements forming aZ-axis sensor mounted on a magnetic sensor in accordance with a sixthembodiment of the present invention.

FIG. 37 A cross-sectional view taken along line IV-IV in FIG. 36.

FIG. 38 Cross-sectional views showing a manufacturing method of themagnetic sensor of the sixth embodiment.

FIG. 39 Cross-sectional views showing the manufacturing method of themagnetic sensor of the sixth embodiment subsequently to FIG. 38.

FIG. 40 Cross-sectional views showing the manufacturing method of themagnetic sensor of the sixth embodiment subsequently to FIG. 39.

FIG. 41 Cross-sectional views showing the manufacturing method of themagnetic sensor of the sixth embodiment subsequently to FIG. 40.

FIG. 42 A plan view showing the structure of giant magnetoresistiveelements forming a Z-axis sensor mounted on a magnetic sensor inaccordance with a seventh embodiment of the present invention.

FIG. 43 A perspective view showing an example of the layout of giantmagnetoresistive elements forming the Z-axis sensor in the seventhembodiment.

FIG. 44 A perspective view showing another example of the layout ofgiant magnetoresistive elements forming the Z-axis sensor in the seventhembodiment.

FIG. 45 A conceptual drawing showing that end portions of slopes ofchannels formed in a thick film are consecutively rounded in amanufacturing method of the magnetic sensor of the seventh embodiment.

DESCRIPTION OF THE REFERENCE NUMERALS

-   A via-   B pad-   C channel forming region-   1 semiconductor substrate-   2 a, 2 b, 2 c, 2 d giant magnetoresistive elements forming an X-axis    sensor-   3 e, 3 f, 3 g, 3 h giant magnetoresistive elements forming a Y-axis    sensor-   4 i, 4 j, 4 k, 41 giant magnetoresistive elements forming a Z-axis    sensor-   5 magneto-sensitive element-   6 bias magnet-   7 wiring layer-   8 channel-   8A, 8E, 8G, 8K, 8M, 8Q, 8S, 8W first slope-   8B, 8D, 8H, 8J, 8N, 8P, 8T, 8V second slope-   21 a conductive portion of via A-   21 b conductive portion of pad B-   27 passivation film-   28 protection film-   31 planation film-   32 passivation film-   33 silicon oxide film-   34 silicon nitride film-   35 thick film-   36 resist film-   37 insulating film-   38 resist film-   40 photomask-   41 fine pattern-   50 slope

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention realizes downsizing and improves a detectionaccuracy with respect to a magnetic sensor using giant magnetoresistiveelements, and it will be described by way of various embodiments inconjunction with the attached drawings.

First Embodiment

FIG. 1 diagrammatically shows a magnetic sensor in accordance with afirst embodiment of the present invention, and it shows the layoutregarding a plurality of giant magnetoresistive elements arranged on asemiconductor substrate.

In FIG. 1, reference numeral 1 designates a semiconductor substratecomposed of silicon, in which semiconductor integrated circuits such asdrive circuits and signal processing circuits, and wiring layers areformed in advance with respect to the magnetic sensor, and on which aplanation film, a passivation film, and a silicon oxide film (not shown)are sequentially formed so as to form a thick film.

An X-axis sensor 2, a Y-axis sensor 3, and a Z-axis sensor 4 arearranged on the thick film of the semiconductor substrate 1, thus makingit possible to detect the intensity of an external magnetic field inthree axial directions. In coordinates axes shown in FIG. 1, the X-axissensor 2 has sensitivity in an X-axis direction, the Y-axis sensor 3 hassensitivity in a Y-axis direction, and the Z-axis sensor 4 hassensitivity in a Z-axis direction.

Specifically, the X-axis sensor 2 is composed of four giantmagnetoresistive elements 2 a, 2 b, 2 c, and 2 d; the Y-axis sensor 3 iscomposed of four giant magnetoresistive elements 3 e, 3 f, 3 g, and 3 h;and the Z-axis sensor 4 is composed of four giant magnetoresistiveelements 4 i, 4 j, 4 k, and 4 l.

The X-axis sensor 2 and the Y-axis sensor 3 are arranged on the planarsurface of the thick film of the semiconductor substrate 1, and theZ-axis sensor 4 is arranged on the slopes of channels formed in thethick film. Details will be described later.

Within the four giant magnetoresistive elements forming the X-axissensor 2, the giant magnetoresistive elements 2 a and 2 b are arrangedto adjoin together approximately in the center of the semiconductorsubstrate 1, and the giant magnetoresistive elements 2 c and 2 d arearranged to adjoin together in the end portion of the semiconductorsubstrate 1. That is, the giant magnetoresistive elements 2 c and 2 dare distant from and arranged opposite to the giant magnetoresistiveelements 2 a and 2 b.

Within the four giant magnetoresistive elements forming the Y-axissensor 3, the giant magnetoresistive elements 3 e and 3 f are arrangedto adjoin together in one end portion of the semiconductor substrate 1,and the giant magnetoresistive elements 3 g and 3 h are arranged toadjoin together in the other end portion of the semiconductor substrate1. That is, the giant magnetoresistive elements 3 e and 3 f are distantfrom and arranged opposite to the giant magnetoresistive elements 3 gand 3 h.

Within the four giant magnetoresistive elements forming the Z-axissensor 4, the giant magnetoresistive elements 4 k and 4 l are arrangedin proximity to the giant magnetoresistive elements 3 e and 3 f, and thegiant magnetoresistive elements 4 i and 4 j are slightly distant fromand arranged adjacent to the giant magnetoresistive elements 2 a and 2b.

The arrangement of the aforementioned giant magnetoresistive elementsforming the X-axis sensor 2, Y-axis sensor 3, and Z-axis sensor 4 isdetermined based on the following rules.

In FIG. 1, dotted lines LA, LB, and LC are imaginary lines for equallydividing the semiconductor substrate 1 into four sections in thelongitudinal direction; and a dotted line LD is an imaginary line forequally dividing the semiconductor substrate 1 in the width direction.In addition, SA designates an intersecting point between the dottedlines LA and LD, and SB designates an intersecting point between thedotted lines LB and LD.

That is, in the X-axis sensor 2, the giant magnetoresistive elements 2 aand 2 b and the giant magnetoresistive elements 2 c and 2 d are arrangedsymmetrically with respect to the intersecting point SA. In the Y-axissensor 3, the giant magnetoresistive elements 3 e and 3 f and the giantmagnetoresistive elements 3 g and 3 h are arranged symmetrically withrespect to the intersecting point SA. In the Z-axis sensor 4, the giantmagnetoresistive elements 4 i and 4 j and the giant magnetoresistiveelements 4 k and 4 l are arranged symmetrically with respect to theintersecting point SB.

The aforementioned giant magnetoresistive elements are formed similar tothe conventionally-known giant magnetoresistive elements. For example,as shown in FIG. 2, each giant magnetoresistive element is constitutedof four magneto-sensitive elements 5 and three bias magnets 6 forelectrically connecting them in series.

The magneto-sensitive elements 5 form a main part of the giantmagnetoresistive element, and they have thin band-like plane shapes. Themagneto-sensitive elements 5 are arranged in parallel in thelongitudinal direction of channels formed in the semiconductor substrate1.

The magneto-sensitive element 5 has a pinned layer whose magnetizationdirection is fixed and a free layer whose magnetization direction variesin response to an external magnetic field. Specifically, it isconstituted of multilayered laminated metals including a conductivespacer layer, a pinned layer, and a capping layer, which aresequentially laminated on a free layer.

For example, the free layer has a three-layered structure including anamorphous magnetic layer composed of cobalt-zirconium-niobium, amagnetic layer composed of nickel-iron, and a magnetic layer composed ofcobalt-iron. The spacer layer is composed of copper; the pinned layerhas a two-layered structure including a ferromagnetic layer composed ofcobalt-iron and a diamagnetic layer composed of platinum-manganese; andthe capping layer is composed of tantalum.

The bias magnets 6 electrically connect the four magneto-sensitiveelements 5 in series, and they apply a bias magnetic field to themagneto-sensitive elements 5, which are thus adjusted in magneticcharacteristics. For example, the bias magnet 6 is constituted oflaminated metals having a two-layered structure including acobalt-platinum-chrome layer and a chrome layer.

Each of the giant magnetoresistive elements 2 a, 2 b, 2 c, 2 d, 3 e, 3f, 3 g, and 3 h forming the X-axis sensor 2 and the Y-axis sensor 3arranged on the planar surface of the semiconductor substrate 1 isconstituted of the four magneto-sensitive elements 5 and the three biasmagnets 6 as shown in FIG. 2, wherein the terminal ends of theexternally-arranged two magneto-sensitive elements 5, which are notconnected to the bias magnets 6, are respectively connected to wiringlayers 7, which are connected to vias (not shown).

FIGS. 3 to 5 show the detailed structure of the giant magnetoresistiveelements 4 i and 4 j within four giant magnetoresistive elements formingthe Z-axis sensor 4. Incidentally, the detailed structure of the othergiant magnetoresistive elements 4 k and 4 l is the same as theaforementioned one; hence, it is not described.

FIG. 3 is a plan view showing the giant magnetoresistive elements 4 iand 4 j; and FIG. 4 is a cross-sectional view taken along line IV-IV inFIG. 3. FIG. 5 is a perspective view diagrammatically showing the layoutof the magneto-sensitive elements 5 and bias magnets 6 included in thegiant magnetoresistive elements 4 i and 4 j.

In FIG. 4, reference numeral 11 designates a thick film composed ofsilicon oxide, which is deposited on the semiconductor substrate 1. Thethick film 11 is partially subjected to cutting so as to form fourV-shaped channels 8.

Each channel 8 is a thin recess having prescribed dimensions, in whichthe depth ranges from 3 μm to 8 μm, the length ranges from 200 μm to 400μm, and the slope width ranges from 3 μm to 16 μm. The angle between theslope and the surface of the thick film 11 ranges from 30° to 80° and ispreferably set to 70°.

Incidentally, FIG. 4 shows that each channel 8 has planar slopes; in theactual manufacturing process, the slope is slightly curved in an outsidedirection (i.e., the upper side of the semiconductor substrate 1).

FIG. 4 shows the four channels 8, in which the magneto-sensitiveelements 5 forming eight giant magnetoresistive elements are arranged atthe center planar positions of the eight slopes adjoining together inthe longitudinal direction. With respect to the giant magnetoresistiveelement 4 j, a bias magnet 6 is formed to extend from themagneto-sensitive element 5, which is formed on one slope of the channel8, to the magneto-sensitive element 5, which is formed on the otherslope of the channel 8, via the bottom, so that the magneto-sensitiveelements 5 adjoining together in the channel 8 are electricallyconnected together. Furthermore, with respect to the giantmagnetoresistive element 41, a bias magnet 6 is formed to extend fromthe magneto-sensitive element 5, which is formed on the slope of onechannel 8, to the magneto-sensitive element 5, which is formed on theslope of the adjacent channel 8, via the top portion, so that themagneto-sensitive elements 8 in the adjacent channels 8 are electricallyconnected together.

As described above, with respect to each giant magnetoresistive element,the four magneto-sensitive elements 5 are electrically connectedtogether by way of the three bias magnets 6.

Similar to the giant magnetoresistive elements forming the X-axis sensor2 and the Y-axis sensor 3 arranged on the planar surface of the thickfilm 11 described above, with respect to each of the giantmagnetoresistive elements forming the Z-axis sensor 4, theexternally-arranged two magneto-sensitive elements 5 are not connectedto the bias magnets 6 but are connected to the wiring layers 7, whichare connected to vias (not shown). The wiring layers 7 are formed usingthe magnet film forming the bias magnets 6 of the giant magnetoresistiveelements. Thus, it is possible to simultaneously form the bias magnets 6and the wiring layers 7 in each giant magnetoresistive element.

As shown in FIG. 2, the sensing directions of the giant magnetoresistiveelements forming the X-axis sensor 2 and the Y-axis sensor 3 cross at aright angle with the magneto-sensitive elements 5 in the longitudinaldirection, and they are set in parallel with the surface of thesemiconductor substrate 1. In addition, the pinning direction of themagneto-sensitive elements 5 and the magnetization direction of a biasmagnetic field of the bias magnets 6 are inclined with respect to thelongitudinal direction of the magneto-sensitive elements 5 by an angleranging from 30° to 60°, preferably by an angle of 45°, and they are inparallel with the surface of the semiconductor substrate 1.

As shown in FIG. 5, the sensing directions of the giant magnetoresistiveelements 4 i and 4 j included in the Z-axis sensor 4 cross at a rightangle with the longitudinal direction of the magneto-sensitive elements5, and they are each set in parallel with the slopes of the channels 8and in an upward direction. In addition, the pinning direction of themagneto-sensitive elements 5 and the magnetization direction of the biasmagnets 6 are inclined with respect to the longitudinal direction of themagneto-sensitive elements 5 by an angle ranging from 30° to 60°,preferably by an angle of 45°, and they are set in parallel with theslopes of the channels 8 and in an upward direction.

As shown in FIG. 6, the sensing directions of the giant magnetoresistiveelements 4 k and 4 l included in the Z-axis sensor 4 cross at a rightangle with the longitudinal direction of the magneto-sensitive elements5, and they are set in parallel with the slopes of the channels 8 and ina downward direction. In addition, the pinning direction of themagneto-sensitive elements 5 and the magnetization direction of a biasmagnetic field of the bias magnets 6 are inclined with respect to thelongitudinal direction of the magneto-sensitive elements 5 by an angleranging from 30° to 60°, preferably by an angle of 45°, and they are inparallel with the slopes of the channels 8 and in a downward direction.

In order to realize the aforementioned sensing directions, a magnetarray is positioned close to the upper side of the semiconductorsubstrate, which is then subjected to heat treatment for three to fivehours at a temperature ranging from 260° C. to 290° C. This method issimilar to the conventionally-known pinning process.

Normally, both the sensing direction and pinning direction of the giantmagnetoresistive element cross at a right angle with the longitudinaldirection of the magneto-sensitive elements 5 and are also set inparallel with the surface of the semiconductor substrate. In the presentembodiment, the sensing direction differs from the pinning direction;hence, it is possible to improve the stability against a high magneticfield.

FIG. 7 shows line-connection methods with respect to the four giantmagnetoresistive elements 2 a, 2 b, 2 c, and 2 d forming the X-axissensor 2, the four giant magnetoresistive elements 3 e, 3 f, 3 g, and 3h forming the Y-axis sensor 3, and the four giant magnetoresistiveelements 4 i, 4 j, 4 k, and 4 l forming the Z-axis sensor 4, wherein thefour giant magnetoresistive elements included in each sensor areconnected together by way of a bridge.

Due to the aforementioned bridge connection, when magnetic fields areapplied in the positive directions of the X-axis, Y-axis, and Z-axis inthe coordinate axes shown in FIG. 1, the outputs of the X-axis sensor 2,Y-axis sensor 3, and Z-axis sensor 4 increase, whereas when magneticfields are applied in the negative directions of the X-axis, Y-axis, andZ-axis, the outputs of the X-axis sensor 2, Y-axis sensor 3, and Z-axissensor 4 decrease.

FIGS. 1 to 6 do not show that the overall surface of the semiconductorsubstrate 1 including all of the giant magnetoresistive elements formingthe X-axis sensor 2, Y-axis sensor 3, and Z-axis sensor 4 is coveredwith a passivation film composed of silicon nitride and a protectionfilm composed of polyimide, by which it is protected from externalenvironments.

FIG. 8 shows the structure of a via formed in the semiconductorsubstrate 1, wherein reference numeral 21 a designates a conductiveportion composed of aluminum forming the via. The conductive portion 21a is electrically connected to a wiring layer, which is formedtherebelow.

The periphery of the surface of the conductive portion 21 a is coveredwith a planation film 22 and a first passivation film 23 as well as thethick film 11. The terminal surfaces of the thick film 11 are slopedsurfaces.

The center of the surface of the conductive portion 21 a is covered witha wiring film 25. The wiring film 25 is connected to the aforementionedwiring layer 7 for the giant magnetoresistive elements. Similar to thewiring layer 7, the wiring film 25 is formed using the magnet filmforming the bias magnets 6. Thus, it is possible to simultaneously formthe wiring film 25 and the bias magnets 6.

Step portions are formed in the wiring film 25 in proximity to theterminal portion of the thick film 11. Due to the manufacturing process,there is a possibility that the wiring film 25 is reduced in thicknessand may be broken at corners of the step portions. For this reason, aprotective conductive film 26 is laminated to cover the step portionsand the center portion.

In the present embodiment, the aforementioned giant magnetoresistiveelement film forming the magneto-sensitive elements 5 is used as theprotective conductive film 26. Thus, it is possible to laminate theprotective conductive film 26 on the wiring film 25 simultaneously withthe formation of the magneto-sensitive elements 5; hence, it is possibleto avoid the breakage of the wiring film 25.

The via having the aforementioned structure is covered with apassivation film 27 composed of silicon oxide and a protection film 28composed of polyimide, by which it is protected from externalenvironments.

The magnetic sensor of the present embodiment functions as a small-sizethree-axial magnetic sensor in that the X-axis sensor 2, Y-axis sensor3, and Z-axis sensor 4 are arranged on a single semiconductor substrate1. In addition, the magneto-sensitive elements 5 of the giantmagnetoresistive elements are formed on the prescribed portions of theslopes of the channels 8 having good planation; hence, it is possible toproduce a magnetic sensor having good sensitivity.

In the end portion of an opening of the via, the protective conductivefilm 26 composed of the giant magnetoresistive element film is laminatedon the wiring film 25 composed of the bias magnet film, thus avoidingbreakage of the wiring film 25 at the corners of the step portions.

In addition, the pinning direction of the magneto-sensitive element 5 isinclined by an angle ranging from 30° to 60° with respect to thelongitudinal direction, thus making it possible to produce a giantmagnetoresistive element having stability against a high magnetic field.

Next, the manufacturing method of the magnetic sensor of the presentembodiment will be described.

Hereinafter, the following description will be mainly given with respectto the manufacturing method regarding vias, pads, and giantmagnetoresistive elements that form the Z-axis sensor 4 and that areformed on the slopes of the channels 8.

FIGS. 9, 10, 11, and 12 show cross-sectional views with regard to a viaA, a pad B, and a channel forming region C in the manufacturing methodof the magnetic sensor of the present embodiment.

First, there is provided a semiconductor substrate 1. That is, wiringlayers and semiconductor integrated circuits such as drive circuits andsignal processing circuits of the magnetic sensor are formed in advanceon the semiconductor substrate 1 composed of silicon.

As shown in FIG. 9( a), a via A and a pad B corresponding to prescribedparts of a wiring layer, which is an uppermost layer, are formed on thesemiconductor substrate 1, wherein the conductive portion 21 a composedof aluminum is formed in the via A, and a conductive portion 21 bcomposed of aluminum is formed in the via B.

A planation film 31 is formed on the aforementioned semiconductorsubstrate 1. For example, the planation film 31 is formed bysequentially laminating a silicon oxide film of 300 nm thickness by wayof the plasma CVD (plasma chemical vapor deposition) method, as SOG filmof 600 nm thickness, and a silicon oxide film of 50 nm thickness, whichis formed by way of the plasma CVD method using the TEOS method, thusforming a planar insulating film.

Next, as shown in FIG. 9( b), the planation film 31 is removed from theconductive portion 21 a of the via A and the conductive portion 21 b ofthe pad B by way of etching, thus making the conductive portions 21 aand 21 b be exposed. Next, as shown in FIG. 9( c), a first passivationfilm 32 (corresponding to the first passivation film 23 shown in FIG. 8)is formed on the overall surface of the semiconductor substrate 1. Forexample, the first passivation film 32 is formed by sequentiallylaminating a silicon oxide film 33 of 250 nm thickness by way of theplasma CVD method and a silicon nitride film 34 of 600 nm thickness byway of the plasma CVD method.

Next, as shown in FIG. 9( d), the silicon nitride film 34 deposited onthe conductive portion 21 a of the via A and the conductive portion 21 bof the pad B is removed by way of etching. At this time, the siliconoxide film 33 is left, while the removing range of the silicon nitridefilm 34 is made smaller than the opening width of the planation film 31.Thus, the terminal portions of the planation film 31 are exposed in theopenings of the via A and the pad B, thus preventing water content frombeing infiltrated into the wiring layer and semiconductor integratedcircuits.

Next, as shown in FIG. 10( a), a thick film 35 of 5 μm thicknesscomposed of silicon oxide is formed by way of the plasma CVD method. Thethick film 35 corresponds to the thick film 11 shown in FIGS. 4 and 8,in which channels 8 are formed.

Next, as shown in FIG. 10( b), a resist film 36 of 3 μm thickness isformed on the overall surface of the thick film 35. Thereafter,prescribed parts of the resist film 36 are removed by way of exposureand development, thus forming a prescribed resist pattern. Thus, channelregions are exposed with respect to the via A, pad B, and channelforming region C.

Next, as shown in FIG. 10( c), the remaining resist film 36 is subjectedto heat treatment for ten minutes or so at a temperature of 150° C.,thus dissolving the resist film 36. Surface tension of the solution,which is produced by way of resist dissolution in heat treatment, causesthe upper surface of the resist film 36 to rise upwardly, whereby theterminal surface is inclined simultaneously. In particular, the resistfilm 36 is transformed into a plurality of projections having linearridgelines in the channel forming region C, wherein the height of thecross-sectional shape reaches about 5 μm.

Thereafter, the resist film 36 and the thick film 35 are subjected todry etching under the prescribed conditions in which the etchingselection ratio between resist and silicon oxide becomes approximatelyone-to-one. The dry etching is performed under the following conditions.

Etching gas: mixed gas of CF₄/CHF₃/N₂/O₂, the mixing ratio of which is60/180/10/100 sccm.

Process pressure: 400 mTorr (53.2 Pa).

RF power: 750 W.

Electrode temperature: 15° C.

Chamber temperature: 15° C.

In the dry etching, as shown in FIG. 11( a), the recessed areas of thevia A and pad B are controlled so as not to become larger than therecessed area of the passivation film 32. Thereafter, the resist film 36remaining on the thick film 35 is removed.

Thus, as shown in FIG. 11( a), a plurality of the channels 8 are formedin the channel forming region of the thick film 35. Next, as shown inFIG. 11( b), the thick film 35 and the silicon oxide film 33 coveringthe conductive portion 21 a of the via A are removed, thus making theconductive portion 21 a be exposed.

Next, a magnet film used for the formation of the bias magnets 6 of thegiant magnetoresistive elements is formed on the overall surface of thesemiconductor substrate 1 by way of sputtering; then, unnecessaryportions are removed by way of resist work and etching. As shown in FIG.11( c), the bias magnets 6 are formed along the slopes of the channels8; at the same time, the wiring film 25 is formed on the conductiveportion 21 a of the via A, thus forming the wiring layer 7 connectingbetween the wiring film 25 and the bias magnets 6 of the giantmagnetoresistive elements.

As described above, the magnet film is formed as a multilayered thinmetal composed of Co—Cr—Pt, for example. At this time, the wiring layer7 corresponding to the bias magnets 6 of the giant magnetoresistiveelements forming the X-axis sensor 2 and the Y-axis sensor 3 is formedon the planar surface of the thick film 35 as well.

In the resist work for the formation of the bias magnets 6, in order toappropriately perform etching on the magnet film in the slopes of thechannels 8, it is preferable that the resist film having a prescribedpattern be subjected to heat treatment, thus inclining the terminalsurfaces of the resist film.

Next, the giant magnetoresistive element film forming themagneto-sensitive elements 5 of the giant magnetoresistive elements isformed on the overall surface of the semiconductor substrate 1 by way ofsputtering. As described above, the giant magnetoresistive element filmis formed as a multilayered thin metal.

Thereafter, the semiconductor substrate 1 is set up above a magnet arrayand is then subjected to heat treatment for three to five hours at atemperature ranging from 260° C. to 290° C., so that the giantmagnetoresistive element film is subjected to a pinning process. Thedetails of the pinning process will be described later.

Thereafter, the giant magnetoresistive element film is subjected toresist work and etching, thus removing unnecessary portions therefrom.As shown in FIG. 12( a), the magneto-sensitive elements 5 are formed onthe slopes of the channels 8, thus completing the formation of the giantmagnetoresistive elements. That is, it is possible to complete theproduction of the Z-axis sensor 4.

At the same time, the giant magnetoresistive element film is left on thewiring film 25 composed of the magnet film, which is formed in advanceon the conductive portion 21 a of the via A, and is used as theprotective conductive film 26. Thus, it is possible to produce thestructure of the via A shown in FIG. 8. At the same time, themagneto-resistive elements 5 are formed on the planar surface of thethick film 35 as well, thus producing giant magnetoresistive elements.This completes the production of the X-axis sensor 2 and the Y-axissensor 3.

Next, as shown in FIG. 12( b), a passivation film 27 of 1 μm thicknesscomposed of silicon nitride is formed by way of the plasma CVD method;and then the protection film 28 composed of polyimide is formed. Theprotection film 28 and the passivation film 27 are removed from the padB, thus forming a recess.

Next, as shown in FIG. 12( c), etching is performed using the protectionfilm 28 as a mask, so that the passivation film 32 and the thick film 35covering the conductive portion 21 b of the pad B are removed, thusmaking the conductive portion 21 b be exposed. This completes theproduction of a magnetic sensor of the present embodiment.

The aforementioned pinning process will be described with reference toFIGS. 13 and 14. FIG. 13 shows the arrangement of magnets in the magnetarray. The magnet array is positioned above the surface of thesemiconductor substrate 1 on which the giant magnetoresistive elementsare formed.

FIG. 13( a) shows the positional relationship between the giantmagnetoresistive elements on the surface of the semiconductor substrate1 and the magnets of the magnet array, wherein S and N representpolarities of magnets positioned opposite to the surface of thesemiconductor substrate 1. FIG. 13( b) shows the polarity andarrangement of the magnets in the cross section taken along a dottedline Q in FIG. 13( a). FIG. 13( c) shows the polarity and arrangement ofthe magnets in the cross section taken along a dotted line R in FIG. 13(a). FIG. 14 is an enlarged view of FIG. 13( b), wherein it shows thedirection of a line of magnetic force exerted on a single giantmagnetoresistive element.

According to the manufacturing method of the magnetic sensor of thepresent embodiment, it is possible to form the X-axis sensor 2, Y-axissensor 3, and Z-axis sensor 4 on the single semiconductor substrate 1,and it is possible to simultaneously produce the via A and pad B. Hence,it is possible to rapidly produce a small-size three-axial magneticsensor by way of a series of processes.

Second Embodiment

Next, a second embodiment of the present invention will be described.

Similar to the first embodiment, the second embodiment is designed suchthat the X-axis sensor 2, Y-axis sensor 3, and Z-axis sensor 4 areformed using giant magnetoresistive elements formed on the semiconductorsubstrate 1; hence, the same reference numerals of the first embodimentare used, and the duplicate description will be omitted.

The second embodiment uses the structures shown in FIGS. 1 and 2. Thestructural difference between the first embodiment and second embodimentwill be described with reference to FIGS. 15 and 16. Similar to theillustrations of FIGS. 3 and 4, FIGS. 15 and 16 show the giantmagnetoresistive elements 4 i and 4 j of the Z-axis sensor 4, whereinreference numerals are denoted with respect to slopes, bottoms, and topportions of the channels 8 adjoining together.

As shown in FIG. 16, each channel 8 is a thin recess having prescribeddimensions, in which the depth ranges from 3 μm to 7 μm, the lengthranges from 250 μm to 300 μm, and the slope width ranges from 3 μm to 8μm. An angle between the slope and the thick film 11 ranges from 30° to80° and is preferably set to 70°.

Incidentally, FIG. 16 is shown such that the channel 8 has planarslopes; however, in the actual manufacturing process, the slope iscurved externally (toward the upper side of the semiconductor substrate1).

With respect to the giant magnetoresistive element 41 shown in FIGS. 15and 16, the magneto-sensitive element 5 is formed on a slope 8 a via thebias magnet 6. The magneto-sensitive element 5 formed on a slope 8 c,which adjoins the slope 8 a via a bottom 8 b, is electrically connectedto the magneto-sensitive element 5 formed on a slope 8 e, which adjoinsthe slope 8 c via a top portion 8 d, via the bias magnet 6. In addition,the magneto-sensitive element 5 is formed on a slope 8 g, which adjoinsthe slope 8 e via a bottom 8 f, via the bias magnet 6.

The detailed structure of the magnetic sensor of the second embodimentis similar to that of the first embodiment shown in FIGS. 5 to 8.

Next, the manufacturing method of the magnetic sensor of the secondembodiment will be described.

The manufacturing process of the first embodiment shown in FIG. 9 isrepeated in the second embodiment; hence, the description thereof willbe omitted.

After completion of the process shown in FIG. 9( a)-(d), as shown inFIG. 17( a), the thick film 35 of 5 μm thickness composed of siliconoxide is formed by way of the plasma CVD method. In the followingprocess, a plurality of the channels 8 are formed using the thick film35.

Next, as shown in FIG. 17( b), the resist film 36 of 5 μm thickness isformed on the overall surface of the thick film 35. Then, as shown inFIG. 17( c), prescribed parts of the resist film 36 are removed by wayof etching, thus making the via A and the pad B be exposed. In addition,prescribed parts of the resist film 36 in the channel forming region Care pressed so as to form a consecutive zigzag shape by way of thestamper method. That is, it is possible to form a plurality ofprojections and channels, wherein the cross-sectional shape of eachprojection is roughly formed in a triangular shape and the top portionthereof is sharpened.

The process for forming a plurality of channels in the resist film 36 inthe channel forming region C by way of the stamper method will bedescribed with reference to FIG. 18.

In the stamper method, at least one pair of alignment marks are formedin advance on both ends of the semiconductor substrate 1 when anuppermost wiring layer is formed on the semiconductor substrate 1.

First, as shown in FIG. 18( a), resist is applied to the overall surfaceof the thick film 35, thus forming the resist film 36. Then, the resistfilm 36 is subjected to heat treatment for five minutes at a temperatureof 120° C. This improves the adhesion between the thick film 35 and theresist film 36, and this makes it possible to easily separate a mold,which is brought into contact with the resist film 36, from the resistfilm 36 in the after-treatment.

Next, as shown in FIG. 18( b) a mold 37 137 is attached to a contactaligner (not shown); then, the semiconductor substrate 1 in which theresist film 36 is formed is positioned at a prescribed position of thecontact aligner, so that the mold 137 is positioned opposite to theresist film 36 formed on the semiconductor substrate 1. In this case,positioning is performed between alignment marks, which are applied tothe semiconductor substrate 1, and alignment marks, which are applied tothe mold 137 at prescribed positions opposite to the semiconductorsubstrate 1, thus establishing precise positioning between thesemiconductor substrate 1 and the mold 137.

The mold 137 is composed of quartz, in which the aforementionedalignment marks are applied at the prescribed positions opposite to thesemiconductor substrate 1. In addition, a plurality of projections 137a, which are consecutively aligned in a zigzag manner (and whose crosssections are each formed in an acute triangular shape having a summit),are formed in the mold 137 at prescribed positions suiting the channelforming regions C of the thick film 35.

Next, as shown in FIG. 18( c), the mold 137 is pressed against theresist film 36 formed on the semiconductor substrate 1. In order torealize easy separation between the resist film 36 and the mold 137 inthe after-treatment, it is preferable that the contact surface(particularly, the lower surface at which the projections 137 a areformed) of the mold 137 in contact with the resist film be covered witha fluorocarbon resin or be subjected to prescribed surface processing(or silicon processing).

Thereafter, the resist film 36 is subjected to heat treatment for tenminutes at a temperature of 150° C., thus dissolving the resist film 36.This makes the terminal surfaces of the via A and the pad B be inclined;and channels suiting the projections 137 a are formed in the channelforming region C.

Incidentally, as the temperature is increased from the room temperature,the resist film 36 becomes softened at 150° C., and then it becomeshardened when the temperature of 200° C. That is, the resist film 36 isnot hardened at the temperature of 150° C. In the present embodiment,the mold 137 is subjected to pressing as the resist film 36 becomessoftened, so that the channel forming region C is deformed in shape tosuit the projections 137 a. Next, while the mold 137 is being pressedagainst the resist film 36 on the semiconductor substrate 1, the resistfilm 36 is cooled, and then the mold 137 is separated, so that theresist film 36 is hardened without changing channel shapes formedtherein. When the heating temperature exceeds 100° C., solvent starts tobe vaporized, thus improving adhesion between the semiconductorsubstrate 1 and the resist film 36.

Next, as shown in FIG. 18( d), the mold 137 is separated from the resistfilm 36. This allows the channels 36 a whose shapes suit the projections137 a of the mold 137 to be formed in the resist film 36. Incidentally,the aforementioned mold 137 can be combined with a photomask; hence, itis possible to simultaneously realize the pattern formation of theresist film 36 and the formation of the channels 36 a.

Next, as shown in FIG. 19( a), the resist film 36 and the thick film 35are subjected to dry etching with an etching selection ratio of 1:1between resist and silicon oxide, thus forming a plurality of channels 8in the thick film 35 and also making the thinned thick film 35 be leftin the via A and the pad B at the same time.

The aforementioned dry etching is performed under the followingconditions.

Etching gas: CF₄/CHF₃/N₂/O₂, mixing ratio 60/180/10/100 sccm.

Pressure: 400 mTorr.

RF Power: 750 W.

Electrode temperature: 15° C.

Chamber temperature: 15° C.

In the aforementioned dry etching, as shown in FIG. 19( a), the recessedwidths of the via A and the pad B are set not to be larger than therecessed width of the passivation film 32. Then, the resist film 36remaining above the thick film 35 is removed.

Thus, as shown in FIG. 19( a), a plurality of channels 8 are formed inthe channel forming region C of the thick film 35. Then, as shown inFIG. 19( b), the thick film 35 and the silicon oxide film 33 coveringthe via A are removed by way of resist work and etching, thus making theconductive portion 21 a of the via A be exposed.

Next, the magnet film used for the formation of the bias magnets 6 ofthe giant magnetoresistive elements is formed on the overall surface ofthe semiconductor substrate 1 by way of sputtering. Then, unnecessaryportions of the magnet film are removed by way of resist work andetching, so that as shown in FIG. 19( c), the bias magnets 6 are formedon the slopes of the channels 8, and the wiring film 25 is formed abovethe conductive portion 21 a of the via A at the same time. In addition,the wiring layer 7 is formed to connect the wiring film 25 and the biasmagnets 6 of the giant magnetoresistive elements.

As described above, a multilayered thin metal is used for the magnetfilm.

In this case, the bias magnets 6 of the giant magnetoresistive elementsforming the X-axis sensor 2 and the Y-axis sensor 3 are formed togetherwith the wiring layer 7 on the planar surface of the thick film 35.

In order to appropriately perform etching on the magnet film withrespect to the slopes of the channels 8 in the resist work used for theformation of the bias magnets 6, the resist film 36 in which aprescribed pattern is formed is subjected to heat treatment, thus makingthe terminal surfaces thereof be inclined.

Next, in order to form the magneto-sensitive elements 5 of the giantmagnetoresistive elements, the giant magnetoresistive element film isformed on the overall surface of the semiconductor substrate 1 by way ofsputtering. The aforementioned multilayered thin metal is used as thegiant magnetoresistive element film.

Then, the semiconductor substrate 1 is set up above a magnet array andis subjected to heat treatment for three to five hours at a temperatureranging from 260° C. to 290° C., thus performing the pinning process onthe giant magnetoresistive element film.

Thereafter, the giant magnetoresistive element film is subjected toresist work and etching, thus removing unnecessary portions therefrom.As shown in FIG. 20( a), the magneto-sensitive elements 5 are formed onthe slopes of the channels 8, thus producing the giant magnetoresistiveelements. This completes the production of the Z-axis sensor 4.

In the above, the giant magnetoresistive element film is left above thewiring film 25 composed of the magnet film formed on the conductiveportion 21 a of the via A, and it is used as the protection conductivefilm 26. Thus, it is possible to form the via A having the structureshown in FIG. 8.

At the same time, the magneto-sensitive elements 5 are formed on theplanar surface of the thick film 35 as well, thus completing theproduction of the giant magnetoresistive elements forming the X-axissensor 2 and the Y-axis sensor 3.

Next, as shown in FIG. 20( b), the passivation film 27 of 1 μm thicknesscomposed of silicon oxide is formed by way of the plasma CVD method, andthe protection film 28 composed of polyimide is formed thereon. Then,the protection film 28 and the passivation film 27 are removed from thepad B, which is thus exposed.

Next, as shown in FIG. 20( c), etching is performed using the protectionfilm 28 as a mask, whereby the silicon oxide film 33 and the thick film35 covering the conductive portion 21 b are removed so as to make thepad B be exposed. This completes the production of the magnetic sensorof the present embodiment.

According to the manufacturing method of the magnetic sensor of thepresent embodiment, it is possible to form the X-axis sensor 2, Y-axissensor 3, and Z-axis sensor 4 on a single semiconductor substrate 1 andto also form the via A and the pad B; it is possible to easily produce asmall-size three-axial magnetic sensor by way of a series of consecutiveprocesses. In addition, the mod 137 having the projections 137 a, whichare shaped to suit the channels 8 formed in the thick film 35, ispressed against the resist film 36 so as to form the channels 8; hence,it is possible to easily form the channels 8 by way of the etching ofthe thick film 35. This improves the planation with respect to theslopes of the channels 8. Since the magneto-sensitive elements formingthe giant magnetoresistive elements are formed on the slopes of thechannels 8, it is possible to form the Z-axis sensor 4 having a fixedsensing direction and a high sensitivity.

In the manufacturing method of the magnetic sensor of the presentembodiment, it is possible to change the process for forming a pluralityof channels 8 in the channel forming region C of the resist film 36formed on the semiconductor substrate 1 as described below.

That is, a photomask 40 composed of gray reticles shown in FIG. 21( a)is used. Numerous fine patterns 41 each having a resolution that issmaller than a resolution of resist forming the resist film 36 areformed in the photomask 40. As shown in FIG. 21( b), the photomask 40 isdesigned such that the number of fine patterns 41 (hereinafter, referredto as a pattern ratio) per unit area is gradually increased from thecenter to both ends of the channel formed in the resist film 36. It ispossible to appropriately adjust the pattern ratio in response to theshape of the channel 8 or the inclination of the slope of the channel 8.

When the resist film 36 is subjected to exposure using theaforementioned photomask 40, regions having higher pattern ratios areeasily exposed, while regions having lower pattern ratios are difficultto expose. That is, as shown in FIG. 22, the resist thickness afterexposure varies in response to the pattern ratio. As a result, as shownin FIG. 23, a channel 36 a whose thickness gradually increases from thecenter to both ends is formed in the resist film 36.

Then, channels are formed in the thick film by way of etching, thusproducing a desired magnetic sensor.

In the aforementioned variation, a positive-type resist is used for theformation of the channel 36 a in the resist film 36 by use of thephotomask 40; however, it is possible to form a negative-type resist bysetting variations of the pattern ratio of the photomask 40 oppositelyto those shown in FIG. 22, whereby a desired channel can be formed inthe resist film 36.

According to the manufacturing method of the magnetic sensor of thepresent embodiment, it is possible to form the X-axis sensor 2, Y-axissensor 3, and Z-axis sensor 4 on a single semiconductor substrate 1, andit is possible to simultaneously form the via A and the pad B. Thismakes it possible to rapidly produce a small-size three-axial magneticsensor by way of a series of consecutive processes.

With respect to the formation of channels, it is possible to form thephotomask 40 having numerous fine patterns 41, the number of which perunit area gradually increases from the center to both ends of thechannel. The photomask 40 is positioned opposite to the resist film 36,which is then subjected to exposure and development, thus forming thedesired channel 36 a. This makes it possible to easily form channelshaving prescribed shapes by way of etching of the thick film 35; hence,it is possible to improve the planation with respect to the slopes ofthe channels. That is, magneto-sensitive elements of giantmagnetoresistive elements are formed on the slopes of the channelshaving improved planation; hence, it is possible to produce a Z-axissensor 4 having a fixed sensing direction and a high sensitivity.

Third Embodiment

A magnetic sensor of a third embodiment is similar to the magneticsensors of the first and second embodiments, although the manufacturingmethod thereof partially differs from the foregoing ones. That is, afterthe foregoing processes of FIGS. 9 and 10, which are described in thefirst embodiment, the resist film 36 and the thick film 35 are subjectedto dry etching in accordance with the reactive ion etching (RIE) methodin high ion etching conditions, so that a plurality of channels 8 areformed in the thick film 35, and at the same time, the thick film 35 isreduced in thickness in connection with the via A and the pad B.

The high ion etching conditions in the reactive ion etching are asfollows:

Etching gas: CF₄/CHF₃/O₂/Ar, mixing ratio of 30/90/50, 100/50, 200 sccm.

Pressure: 100 to 400 mTorr.

RF Power: 750 to 1200 W.

Under the aforementioned high ion etching conditions, it is possible torealize the shape shown in FIG. 19( a) used in the second embodiment.Then, as described in the second embodiment, the foregoing processesshown in FIGS. 19( b), (c), and FIGS. 20( a), (h), (c) are performed.

According to the third embodiment, it is possible to form the X-axissensor 2, Y-axis sensor 3, and Z-axis sensor 4 on a single semiconductorsubstrate 1, and it is possible to form the via A and the pad B at thesame time; hence, it is possible to rapidly produce a small-sizethree-axial magnetic sensor by way of a series of consecutive processes.In addition, dry etching is performed in accordance with the reactiveion etching method in the high ion etching conditions, whereby it ispossible to form a plurality of channels 8 whose cross-sectional shapesare connected in a zigzag manner, in the thick film 35 in the channelforming region C; hence, it is possible to improve the planation withrespect to the slopes of the channels 8.

Incidentally, after the completion of the foregoing processes shown inFIGS. 9( a) to (d), it is possible to perform processes shown in FIGS.24( a) and (b).

That is, as shown in FIG. 24( a), the thick film of 5 μm thicknesscomposed of silicon oxide is formed by way of the plasma CVD method.Herein, a plurality of projections 35 a each having a rectangularcross-sectional shape are formed only in the channel forming region C.

Next, as shown in FIG. 24( b), silicon oxide is deposited on the thickfilm 35 by way of the high-density plasma CVD method, thus forming aninsulating film 37 whose thickness ranges from 3 μm to 5 μm. Herein, theinsulating film 37 having a planar surface is formed in connection withthe via A and the pad B, whereas the projections 37 a having slopes areformed in the channel forming region C.

In the high-density plasma CVD method, silicon oxide is subjected tosynthesis and deposition by use of high-density plasma (e.g., anelectron density ranging from 1×10⁹/cm³ to 5×10¹⁰/cm³), and at the sametime, prescribed parts of the deposited silicon oxide are subjected toplasma etching.

By the aforementioned high-density plasma CVD method, the insulatingfilm 37 composed of silicon oxide is deposited on the plurality ofprojections 35 a of the thick film 35, so that it projects upwardly incomparison with the periphery thereof. Upper corners of the insulatingfilm 37 are subjected to cutting in the channel forming region C, sothat the projections 37 a having slopes are formed.

The high-density plasma CVD method is performed under the followingconditions.

Monosilane flow: 50 to 150 sccm.

Oxygen flow: 100 to 200 sccm.

Pressure: 1 to 10 Pa.

Temperature: 250° C. to 450° C.

High frequency output: 2 kW to 5 kW.

Frequency: 10 MHz to 20 MHz.

Thereafter, the thick film 35 and the insulating film 37 are entirelysubjected to back-etching in accordance with the reactive ion etchingmethod, plasma dry etching method, and ion milling method, thus formingprojections having slopes in the thick film 35 (see the channel formingregion C shown in FIG. 19). As described above, a plurality of channelsare formed. Then, the thick film 35 is subjected to dry etching by usingthe resist film 36, which has opening patterns in connection with thevia A and the pad B, as a mask, thus reducing the thickness of the thickfilm 35 remaining in the via A and the pad B.

The following etching conditions are adapted to the reactive ion etchingmethod, which is performed to form a plurality of the channels 8.

Etching gas: CF₄/CHF₃/O₂/Ar, mixing ratio of 30/90/50, 100/50, and 20sccm.

Pressure: 100 to 400 mTorr.

RF Power: 750 to 1200 W.

In addition, the following conditions are adapted to the plasma etchingmethod, which is performed to form a plurality of the channels 8.

Etching gas: Ar, 100 sccm.

RF Power: 1200 W.

Pressure: 100 mTorr.

Electrode temperature: 100° C.

Furthermore, the following conditions are adapted to the ion millingmethod, which is performed to form a plurality of the channels 8.

Ar gas: 4 to 10 sccm.

Pressure: 1×10⁻⁴ to 1×10⁻³ Torr.

Acceleration voltage: 50 to 1000 W.

Current: 150 to 350 mA.

Electrode angle (i.e., an angle formed between the propagation directionof acceleration particles and the normal line of a wafer): 0±45°.

After the aforementioned process, the foregoing processes shown in FIGS.19 and 20, which are described in the second embodiment, are performed.

Fourth Embodiment

A magnetic sensor of a fourth embodiment is similar to the foregoingmagnetic sensors of the first and second embodiments, although itpartially differs from the foregoing ones in terms of the manufacturingmethod. Incidentally, unlike the foregoing structures shown in FIGS. 4and 16, the fourth embodiment is designed such that, as shown in FIG.25, an etching stopper layer 12 composed of a passivation film and aninsulating film is inserted between the semiconductor substrate 1 andthe thick film 11.

The manufacturing method of the magnetic sensor of the fourth embodimentwill be described.

Similar to the first embodiment, after completion of the foregoingprocesses shown in FIGS. 9 and 10, the resist film 36 and the thick film35 are subjected to dry etching by using the silicon nitride film 34 toform the upper layer of a passivation film 32 as an etching stopper asshown in FIG. 11( a), thus forming a plurality of the channels 8 in thethick film 35 and simultaneously reducing the thickness of the thickfilm 35 remaining in the via A and the pad B.

Since the silicon nitride film 34 is used as an etching stopper, dryetching is completed when the silicon nitride film 34 is exposed in thechannel forming region C.

That is, reactive ion etching (RIE) is performed under the followingconditions.

Etching gas: C₄F₈/Ar/CH₂F₂, mixing ratio of 7/500/4 sccm.

Gas pressure: 50 mTorr.

RF Power: 1500 W.

Since the dry etching is performed under the aforementioned conditions,it is possible to increase the etching selection ratio between resistforming the resist film 36 and silicon oxide forming the thick film 35;hence, it is possible to use the silicon nitride film 34 as an etchingstopper. Thus, as shown in FIG. 11( a), the plurality of channels 8formed in the thick film 35 are recessed toward the silicon nitride film34. The etching selection ratio can be set to “6”, for example.

Then, similar to the first embodiment, the foregoing processes shown inFIGS. 11( b), (c), and FIGS. 12( a), (b), (c) are performed.

Next, the manufacturing method of the magnetic sensor of the fourthembodiment will be described.

First, similar to the first embodiment, the foregoing processes shown inFIGS. 9( a) to (d) are performed. Then, as shown in FIG. 26( a), theinsulating film 37 of 0.2 μm thickness is formed by way of sputtering.The insulating film 37 is composed of aluminum oxide (Al₂O₃), boronnitride (BN), and diamond-like carbon. As the insulating film, it ispossible to use one such as a silicon nitride film and a silicon oxidefilm having an etching rate lower than that of the thick film 35.

Next, as shown in FIG. 26( b), a resist film 38 of 3 μm thickness isformed on the overall surface of the insulating film 37. Then, as shownin FIG. 26( c), prescribed parts of the resist film 38 are removed byway of etching, thus forming a prescribed resist pattern. The resistpattern has openings only corresponding to the via A and the pad B, bywhich the insulating film 37 is exposed.

Next, as shown in FIG. 27( a), the insulating film 37 is removed fromprescribed regions corresponding to the via A and the pad B by way ofion milling, thus making the silicon oxide film 33 be exposed. Then, asshown in FIG. 27( b), the resist film 38 is removed.

Next, as shown in FIG. 28( a), the thick film 35 of 5 μm thicknesscomposed of silicon oxide is formed by way of the plasma CVD method.Then a plurality of the channels 8 are formed in the thick film 35.

Next, as shown in FIG. 28( b), the resist film 36 of 3 μm thickness isformed on the overall surface of the thick film 35. Then, prescribedparts of the resist film 36 are removed by way of etching, thus forminga prescribed resist pattern. The resist pattern has openingscorresponding to the channels 8 formed in the channel forming region Cand openings corresponding to the regions of the via A and pad B.

Next, as shown in FIG. 28( c), the remaining resist film 36 is subjectedto heat treatment for ten minutes at a temperature of 150° C., thusdissolving the resist film 36. Due to the surface tension of a solutionthat is produced by dissolution of resist in the heat treatment, theupper surface of the resist film 36 rises up, and the terminal surfacethereof slopes. In particular, a plurality of projections having linearridgelines are formed in the resist film 36, wherein the height thereofis 5 μm or so.

Next, as shown in FIG. 29( a), the resist film 36 and the thick film 35are subjected to dry etching by using the insulating film 37 as anetching stopper under prescribed conditions realizing the etchingselection ratio of 1:1 between the resist and silicon oxide, thusforming a plurality of channels 8 in the thick film 35 andsimultaneously reducing the thickness of the thick film 35 remaining inthe via A and the pad B.

That is, reactive ion etching (RIE) is performed under the followingconditions.

Etching gas: CF₄/CHF₃/N₂, mixing ratio of 30/90/5 sccm.

Gas pressure: 200 mTorr.

RF Power: 750 W.

Since the aforementioned dry etching conditions realize setting of theetching selection ratio between resist forming the resist film 36 andsilicon oxide forming the thick film 35 at 1:1, it is possible to usethe insulating film 37 as an etching stopper. Thus, as shown in FIG. 29(a), each channel 8 is formed by recessing the thick film 35 toward theinsulating film 37.

In the aforementioned dry etching, as shown in FIG. 29( a), the recessedwidths at the via A and the pad B are controlled so as not to becomelarger than the recessed width of the first passivation film 32. Then,the resist film 36 remaining on the thick film 35 is removed.

Thus, as shown in FIG. 29( a), a plurality of the channels 8 are formedin the thick film 35 in the channel forming region C. Then, as shown inFIG. 29( b), the thick film 35 and the silicon oxide film 33 coveringthe conductive portion 21 a of the via A are removed by way of etching,thus making the conductive portion 21 a be exposed.

Thereafter, the magnet film forming the bias magnets 6 of the giantmagnetoresistive elements is formed on the overall surface of thesemiconductor substrate 1 by way of sputtering; unnecessary portions areremoved by way of resist work and etching; as shown in FIG. 29( c), thebias magnets 6 are formed on the slopes of the channels 8; at the sametime, the wiring film 25 is formed on the conductive portion 21 a of thevia A; furthermore, the wiring layer 7 is formed to connect the wiringfilm 25 and the bias magnets 6 of the giant magnetoresistive elementstogether.

A multilayered thin metal is used for the magnet film.

In addition, the bias magnets 6 of the giant magnetoresistive elementsforming the X-axis sensor 2 and the Y-axis sensor 3 as well as thewiring layer 7 are formed on the planar surface of the thick film 35.

In order to appropriately perform etching on the magnet film inconnection with the slopes of the channels 8 in the resist work for theformation of the bias magnets 6, the resist film 36, in which aprescribed resist pattern is already formed, is subjected to heattreatment, thus making the terminal surfaces of the resist film 36incline.

Then, the giant magnetoresistive element film forming themagneto-sensitive elements 5 of the giant magnetoresistive elements isformed on the overall surface by way of sputtering. A multilayered thinmetal is used for the giant magnetoresistive element film.

The semiconductor substrate 1, in which the aforementioned giantmagnetoresistive element film is formed, is set up above a magnet arrayand is then subjected to heat treatment for three to five hours at atemperature ranging from 260° C. to 290° C., thus subjecting the giantmagnetoresistive element film to the pinning process.

Next, the giant magnetoresistive element film is subjected to resistwork and etching so as to remove unnecessary portions therefrom, so thatthe magneto-sensitive elements 5 are formed on the slopes of thechannels 8 as shown in FIG. 30( a), thus completing the production ofthe giant magnetoresistive elements. This completes the production ofthe Z-axis sensor 4.

At the same time, a part of the giant magnetoresistive element filmremains on the wiring film 25 composed of the magnet film, which isformed in advance above the conductive portion 21 a of the via A, and isused as the protective conductive film 26. Thus, it is possible toproduce the via A having the structure shown in FIG. 8.

At the same time, the magneto-sensitive elements 5 are formed on theplanar surface of the thick film 35 as well, thus forming the giantmagnetoresistive elements. This completes the production of the X-axissensor 2 and the Y-axis sensor 3.

Next, as shown in FIG. 30( b), the passivation film 27 of 1 μm thicknesscomposed of silicon nitride is formed by way of the plasma CVD method;furthermore, the protection film 28 composed of polyimide is formed.Then, the protection film 28 and the passivation film 27 are removedfrom the region corresponding to the pad B, which is thus exposed.

Lastly, as shown in FIG. 30( c), etching is performed using theprotection film 28 as a mask so as to remove the silicon oxide film 33and the thick film 35 covering the conductive portion 21 b of the pad B,thus making the conductive portion 21 b of the pad B be exposed. Thiscompletes the production of the magnetic sensor of the fourthembodiment.

According to the manufacturing method of the magnetic sensor of thefourth embodiment, it is possible to form the X-axis sensor 2, Y-axissensor 3, and Z-axis sensor 4 on a single semiconductor substrate 1 andto simultaneously form the via A and the pad B; hence, it is possible torapidly produce a small-size three-axial magnetic sensor by way of aseries of processes. Since the resist film 36 and the thick film 35 aresubjected to etching by using the insulating film 37 formed on thepassivation film 32 as an etching stopper, it is possible to form aplurality of channels 8 by recessing the insulating film 37 toward thethick film 35. This forms slopes having prescribed inclination angles inthe thick film 35; hence, it is possible to produce a magnetic sensorusing giant magnetoresistive elements realizing a sensitivity in avertical direction perpendicular to the surface of the semiconductorsubstrate 1. The fourth embodiment is characterized in that the channelformation can be easily controlled in the depth direction due to theformation of the insulating film 37 on the passivation film 32.

Fifth Embodiment

A magnetic sensor of a fifth embodiment of the present invention has astructure similar to that of the first embodiment; and differencestherebetween will be described with reference to FIGS. 31 to 33.

FIG. 31 is a plan view showing the giant magnetoresistive elements 4 iand 4 j;

FIG. 32 is a cross-sectional view taken along line IV-IV in FIG. 31; andFIG. 33 is an enlarged cross-sectional view of an area encompassed bydotted lines in FIG. 32.

In FIG. 32, the thick film 11 composed of silicon oxide is formed on thesemiconductor substrate 1; and the thick film 11 is partially cut so asto form four channels, each having a V-shape, in parallel.

The channel 8 is a thin recess having prescribed dimensions, wherein thedepth ranges from 3 μm to 8 μm, the length ranges from 200 μm to 400 μm,and the slope width ranges from 3 μm to 16 μm.

The slopes of the channels 8 are composed of first slopes 8A, 8E, and 8Gon the upper side as well as second slopes 8B, 8D, and 8H on the lowerside, wherein they have different inclination angles, which range from60° to 80° with respect to the surface of the thick film 11, and whereinthe second slopes are greater than the first slopes in inclinationangles.

FIG. 32 shows that each slope of the channel 8 is formed by the firstand second slopes, both of which are planar; however, in the actualmanufacturing process, each slope of the channel 8 is slightly bentexternally.

As shown in FIG. 33, each slope of the channel 8 is formed so as tosatisfy the relationship of θ₁>θ₂, wherein θ₁ represents an angle(0°<θ₁<90°) formed between the second slope 8D and the silicon nitridefilm 34 (or the semiconductor substrate 1), and θ₂ represents an angle(0°<θ₂<90°) formed between the first slope 8E and the silicon nitridefilm 34 (or the semiconductor substrate 1).

In addition, a magneto-sensitive element 5 of the giant magnetoresistiveelement is formed on the second slope 8D having a larger inclinationangle θ₁.

Since the magneto-sensitive element 5 of the giant magnetoresistiveelement is formed on the second slope 8D having a larger inclinationangle θ₁ as described above, it is possible to adjust the sensingdirection of the Z-axis sensor 4 and to increase the sensitivitythereof.

As described above, the magneto-sensitive elements 5 of the giantmagnetoresistive elements are formed on the eight slopes adjoiningtogether in the four channels 8 shown in FIG. 32 such that they are eachformed along the lower-side second slope in the longitudinal directionand at the center having good planation.

With respect to the giant magnetoresistive element 41, themagneto-sensitive element 5 formed on the second slope 8D iselectrically connected to the magneto-sensitive element 5 formed on thesecond slope 8H via the bias magnet 6 extending over the first slope 8E,top portion 8F, and its adjacent first slope 8G

With respect to the giant magnetoresistive element 4 j, themagneto-sensitive element formed on the second slope 8N is electricallyconnected to the magneto-sensitive element 5 formed on the adjacentsecond slope 8P via the bias magnet 6 over the bottom 8O.

Next, the manufacturing method of the magnetic sensor of the fifthembodiment will be described.

Similar to the first embodiment, the foregoing processes shown in FIGS.9( a) to (d) and FIGS. 10( a) to (c) are performed.

Then, as shown in FIG. 34( a), a plurality of channels are formed in thethick film 35 in the channel forming region C, wherein each slope of thechannel 8 is bent in the middle thereof due to the aforementioned dryetching, so that the second slope lying in proximity to the siliconnitride film 34 is connected to the first slope lying in proximity tothe top portion.

That is, each slope of the channel 8 is formed to satisfy therelationship of θ₁>θ₂, wherein θ₁ represents an angle (0°<θ₁<90°) formedbetween the second slope and the silicon nitride film 34 (or thesemiconductor substrate 1), and θ₂ represents an angle (0°<θ₂<90°)formed between the first slope and the silicon nitride film 34 (or thesemiconductor substrate 1).

In the present embodiment, the magneto-sensitive element 5 of the giantmagnetoresistive element is formed on the second slope having a largerinclination angle θ₁ measured from the semiconductor substrate 1.Incidentally, the angles θ₁ and θ₂ vary depending upon the etchingconditions used for the formation of the channels 8, wherein it ispreferable that the angle θ₁ be increased as much as possible and be setclose to 90°.

Next, as shown in FIG. 34( b), the thick film 35 and the silicon oxidefilm 33 covering the conductive portion 21 a of the via A are removed byway of etching, thus making the conductive portion 21 a be exposed.

Next, the magnet film forming the bias magnets 6 of the giantmagnetoresistive elements is formed on the overall surface of thesemiconductor substrate 1 by way of sputtering; then, unnecessaryportions are removed by way of resist work and etching. As a result, asshown in FIG. 34( c), the bias magnets 6 are formed on the second slopesof the channels 8; at the same time, the wiring film 25 is formed abovethe conductive portion 21 a of the via A; and the wiring layer 7 isformed to connect together the wiring film 25 and the bias magnets 6 ofthe giant magnetoresistive elements. A multilayered thin metal is usedfor the magnet film.

In addition, the bias magnets 6 of the giant magnetoresistive elementsforming the X-axis sensor 2 and the Y-axis sensor 3 as well as thewiring layer 7 are formed on the planar surface of the thick film 35 aswell.

In order to appropriately perform etching on the magnet film on thesecond slopes of the channels 8 in the resist work used for theformation of the bias magnets 6, the resist film, in which a prescribedresist pattern is formed, is subjected to heat treatment, thus makingthe terminal surfaces of the resist film incline.

Next, the giant magnetoresistive element film forming themagneto-sensitive elements 5 of the giant magnetoresistive elements isformed on the overall surface by way of sputtering. A multilayered thinmetal is used for the giant magnetoresistive element film.

Then, the semiconductor substrate 1 is set in a position in proximity toa magnet array and is then subjected to heat treatment for three to fivehours at a temperature ranging from 260° C. to 290° C., thus subjectingthe giant magnetoresistive element film to the pinning process.

Thereafter, the giant magnetoresistive element film is subjected toresist work and etching so as to remove unnecessary portions therefrom,so that, as shown in FIG. 35( a), the magneto-sensitive elements 5 areformed on the second slopes of the channels, thus producing giantmagnetoresistive elements. This completes the production of the Z-axissensor 4.

In addition, the giant magnetoresistive element film remaining on thewiring film 25 composed of the magnet film, which is formed in advanceabove the conductive portion 21 a of the via A, is used for theprotective conductive film 26. Thus, it is possible to produce the via Ahaving the structure shown in FIG. 8. At the same time, themagneto-sensitive elements 5 are also formed on the planar surface ofthe thick film 35, thus producing giant magnetoresistive elements. Thiscompletes the production of the X-axis sensor 2 and the Y-axis sensor 3.

Next, as shown in FIG. 35( b), the passivation film 27 of 1 μm thicknesscomposed of silicon nitride is formed by way of the plasma CVD method;and the protection film 28 composed of polyimide is formed thereon. Theprotection film 28 and the passivation film 27 are removed from theprescribed region corresponding to the pad B, which is thus exposed.

Next, as shown in FIG. 35( c), etching is performed using the protectionfilm 28 as a mask so as to remove the silicon oxide film 33 and thethick film 35 covering the conductive portion 21 b of the pad B, so thatthe pad B is completely exposed. This completes the production of themagnetic sensor of the present embodiment.

Sixth Embodiment

Next, a sixth embodiment of the present invention will be described,wherein the constituent elements similar to those of the firstembodiment are not described.

Similar to the first embodiment, the sixth embodiment is designed suchthat a plurality of giant magnetoresistive elements are formed on thesemiconductor substrate 1 so as to form the X-axis sensor 2, Y-axissensor 3, and Z-axis sensor 4, wherein differences are introduced intothe giant magnetoresistive elements forming the Z-axis sensor 4.

FIG. 36 is a plan view showing the giant magnetoresistive elements 4 iand 4 j forming the Z-axis sensor 4; and FIG. 37 is a cross-sectionalview taken along line IV-IV in FIG. 36.

In FIG. 37, the thick film 11 composed of silicon oxide is formed on thesemiconductor substrate 1. Prescribed parts of the thick film 11 aresubjected to cutting, thus forming six channels 8, each having aV-shape, in parallel. Each channel 8 is a thin recess having prescribeddimensions, wherein the depth ranges from 3 μm to 7 μm, the lengthranges from 250 μm to 300 μm, and the slope width ranges from 3 μm to 8μm, and wherein an angle formed between the slope and the thick film 11ranges from 60° to 80° and is preferably set to 70°. Incidentally, dueto the actual manufacturing process, each slope of the channel 8 is notformed to be planar but is curved externally.

In FIG. 37, eight of the magneto-sensitive elements 5 forming giantmagnetoresistive elements are formed with respect to eight channels offour adjacent channels, which are positioned in the center among sixchannels 8 adjoining together, wherein they are each formed at thecenter having good planation along the longitudinal direction.

With respect to the giant magnetoresistive element 41, themagneto-sensitive element 5 formed on the slope of the channel 8 iselectrically connected to the magneto-sensitive element 5 formed on theslope of the adjacent channel 8 via the bias magnet 6 extending over thetop portion. With respect to the giant magnetoresistive element 4 j, themagneto-sensitive element 5 formed on one slope of the channel 8 iselectrically connected to the magneto-sensitive element 5 formed on theother slope of the channel 8 via the bias magnet 6 extending over thebottom portion.

In the present embodiment, as shown in FIGS. 36 and 37, a total of fourfirst dummy slopes 91 are formed using the two channels 8, which areformed externally to the four channels 8 in which the giantmagnetoresistive elements are formed. In addition, both ends of thetotal of twelve slopes formed in the six channels 8 are extended in thelongitudinal direction and are used to form a total of twenty-foursecond dummy slopes 92 via gaps therebetween.

The first dummy slopes 91 are each shaped in a similar manner to theother slopes and are each formed in a rectangular shape in plan view,wherein the inclination angles thereof are reduced. As shown in FIG. 36,the second dummy slopes 92 are each formed in a trapezoidal shape inplan view but are reduced in widths thereof toward both ends of eachchannel 8, wherein the inclination angles thereof are reduced.

The magneto-sensitive elements 5 and the bias magnets 6 forming thegiant magnetoresistive elements are not formed on the first dummy slopes91 and the second dummy slopes 92. Both the first dummy slopes 91 andthe second dummy slopes 92 are formed simultaneously with the formationof the channels 8. Details will be described later.

In the present embodiment, even when peripheral shapes and inclinationangles of slopes vary due to the formation of the channels 8 inassociation with the formation of the first dummy slopes 91 and thesecond dummy slopes 92, it is possible to avoid variations in theperformance of giant magnetoresistive elements because no giantmagnetoresistive element is formed in the corresponding region; hence,it is possible to produce giant magnetoresistive elements having goodmagnetism sensing characteristics. This reliably produces a Z-axissensor having good performance.

In addition, the pinning direction of the magneto-sensitive element 5 isinclined by an angle ranging from 30° to 60° in the longitudinaldirection, whereby it is possible to improve the stability against ahigh magnetic field with respect to the giant magnetoresistive elements.

Next, the manufacturing method of the magnetic sensor of the presentembodiment will be described.

First, as shown in FIG. 38( a), the planation film 31 is formed on thesemiconductor substrate 1. The planation film 31 is formed bysequentially laminating a silicon oxide film of 300 nm thickness, a SOGfilm of 600 nm thickness, and a silicon oxide film of 50 nm thicknesscomposed of triethoxy silane by way of the plasma CVD method.

Next, as shown in FIG. 38( b), the passivation film 32 is formed on theoverall surface of the semiconductor substrate 1. The passivation film32 is formed by laminating a silicon oxide film of 250 nm thickness anda silicon nitride film of 600 nm thickness by way of the plasma CVDmethod.

Next, as shown in FIG. 39( a), the thick film 35 of 5 μm thicknesscomposed of silicon oxide is formed by way of the plasma CVD method. Inthe after-treatment, a plurality of channels 8 are formed in the thickfilm 35.

Next, as shown in FIG. 39( b), the resist film 36 of 3 μm thickness isformed on the overall surface of the thick film 35. Then, prescribedparts of the resist film 36 are removed by way of etching, thus forminga prescribed resist pattern. The resist pattern has openings atprescribed regions corresponding to channels formed in the channelforming region. In the present embodiment, the resist pattern isappropriately processed at the prescribed regions thereof in order torealize the simultaneous formation of the first dummy slopes 91 and thesecond dummy slopes 92.

Next, as shown in FIG. 39( c), the remaining resist film 36 is subjectedto heat treatment for ten minutes at a temperature of 150° C., thusdissolving the resist film 36. The upper surface of the resist film 36rises upwardly due to the surface tension of a solution, which isproduced following the resist dissolution in the heat treatment, thusmaking the terminal surfaces thereof incline. Thus, it is possible toform a plurality of projections having linear ridgelines, the height ofwhich is set to 5 μm or so.

Thereafter, the resist film 36 and the thick film 35 are subjected todry etching at an etching selection ratio of 1:1 between resist andsilicon oxide. The dry etching is performed under the followingconditions.

Etching gas: CH₄/CHF₃/N₂/O₂, mixing ration of 60/180/10/100 sccm.

Pressure: 400 mTorr (53.2 Pa).

RF Power: 750 W.

Electrode temperature: 15° C.

Chamber temperature: 15° C.

Then, the resist film 36 remaining above the thick film 35 is removed.

Thus, as shown in FIG. 40( a), it is possible to form a plurality ofchannels 8 in the thick film 35 in the channel forming region.

Next, the magnet film forming the bias magnets 6 of the giantmagnetoresistive elements is formed on the overall surface of thesemiconductor substrate 1 by way of sputtering, and then unnecessaryportions thereof are removed by way of resist work and etching. Thus, asshown in FIG. 40( b), it is possible to appropriately form the biasmagnets 6 and the wiring film therefor on the slopes of the channels 8except for the first dummy slopes 91 and the second dummy slopes 92.

A multilayered thin metal is used for the magnet film.

In addition, the bias magnets 6 of the giant magnetoresistive elementsforming the X-axis sensor 2 and the Y-axis sensor 3 as well as thewiring layer 7 therefor are formed on the planar surface of the thickfilm 35.

In order to appropriately perform etching on the magnet film on theslopes of the channels 8 in the resist work for the formation of thebias magnets 6, the resist film 36, in which a prescribed resist patternis formed, is subjected to heat treatment, thus making the terminalsurfaces thereof incline.

Next, the giant magnetoresistive element film forming themagneto-sensitive elements 5 of the giant magnetoresistive elements isformed on the overall surface of the semiconductor substrate 1 by way ofsputtering. A multilayered thin metal is used for the giantmagnetoresistive element film.

The aforementioned semiconductor substrate 1 is set in a position closeto a magnet array and is then subjected to heat treatment for three tofive hours at a temperature ranging from 260° C. to 290° C., thussubjecting the giant magnetoresistive element film to the pinningprocess.

Thereafter, the giant magnetoresistive element film is subjected toresist work and etching, thus removing unnecessary portions therefrom;hence, as shown in FIG. 41( a), the magneto-sensitive elements 5 areformed on the slopes of the channels except for the first dummy slopes91 and the second dummy slopes 92, thus forming giant magnetoresistiveelements. This completes the production of the Z-axis sensor 4.

At the same time, the magneto-sensitive elements 5 are formed on theplanar surface of the thick film 35 as well, thus forming giantmagnetoresistive elements. This completes the production of the X-axissensor 2 and the Y-axis sensor 3.

Next, as shown in FIG. 41( b), the passivation film 27 of 1 μm thicknesscomposed of silicon nitride is formed by way of the plasma CVD method;furthermore, the protection film 28 composed of polyimide is formed.This completes the production of the magnetic sensor of the presentembodiment.

In the present embodiment, a plurality of channels 8 are formed in thethick film, and the first dummy slopes 91 and the second dummy slopes 92are formed using similar channel shapes. Herein, channel shapes are notnecessarily formed; that is, a plurality of bank-like projections areformed on the semiconductor substrate 1, and the slopes thereof areused, for example.

The formation of the aforementioned projection is realized by the samemethod as the formation of the channels 8. That is, as shown in FIG. 39(c), the resist film 36 is subjected to patterning and heat treatment,and then the resist film 36 and the thick film 35 are subjected toplasma etching with an etching selection ratio of 1:1 between resist andsilicon oxide.

The plasma etching is performed to make the surface of the thick film 35be planar except for the prescribed regions used for the formation ofchannels 8; and then a major part of the thick film 35 is removed so asto form a plurality of bank-like projections.

With respect to the formation of projections, a prescribed resistpattern is applied to the resist film 36 so as to produce projectionsrealizing the first dummy slopes 91 and the second dummy slopes 92.

Seventh Embodiment

A magnetic sensor of a seventh embodiment is similar to the firstembodiment; hence, the duplicate description is omitted, and differencestherebetween are described below.

FIG. 42 is a plan view showing giant magnetoresistive elements 4 i and 4j forming a Z-axis sensor 4. Incidentally, a cross-sectional view takenalong line IV-IV in FIG. 42 is identical to FIG. 4. FIG. 43 is aperspective view showing the layout of the giant magnetoresistiveelements 4 i and 4 j; and FIG. 44 is a perspective view showing thelayout of the giant magnetoresistive elements 4 k and 4 l.

In the present embodiment, the terminal portions of the channels 8extending in the longitudinal direction are curved slopes havingsemi-circular shapes. When the channels 8 are formed by way of etching,the resist film is subjected to patterning and is shaped by heating torealize the shapes of the channels 8. In this case, since the terminalportions of the channel slopes of the resist pattern in the longitudinaldirection are shaped so as to be semi-circular, it is possible toprevent the widths of the terminal portions of the slopes after heattreatment from being decreased. Incidentally, the terminal portions ofthe channel slopes are not necessarily shaped to be semi-circular;hence, it is possible to employ other shapes having prescribed degreesof roundness.

Incidentally, the manufacturing method of the magnetic sensor of thepresent embodiment is similar to the foregoing ones used in the first tosixth embodiments; hence, the description thereof will be omitted. Inthe channel formation, after the heat treatment, slopes 50 are formed asshown in FIG. 45. That is, each slope 50 is formed so as to have thesame width in the longitudinal direction ranging from the center to theends, thus realizing a uniform plane shape and inclination angle. Inaddition, the ends of the slopes 50 in the longitudinal direction areconnected as curved slopes; hence, adjacently opposite slopes areconnected, and the end portion of the channel is shaped so as to besemi-circular.

INDUSTRIAL APPLICABILITY

The present invention is designed such that the thick film formed on thesemiconductor substrate is subjected to cutting so as to form channelsor projections having linear ridgelines, in which giant magnetoresistiveelements forming a Z-axis sensor are formed on the slopes; hence, it isapplicable to small-size magnetic sensors such as three-axial sensorseach formed on a single semiconductor substrate.

In addition, the present invention is applicable to electronic compassesinstalled in various portable electronic devices such as portabletelephones.

1.-14. (canceled)
 15. A manufacturing method for a magnetic sensorcomprising: forming a planation layer that provides planation bycovering a wiring layer of a semiconductor substrate; forming apassivation film on the planation layer; forming a thick film on thepassivation film; forming a resist film on the thick film; partiallyremoving the resist film; performing etching on the resist film and thethick film, thus forming a plurality of channels in the thick film;forming an opening in the thick film to form a via; forming a wiringfilm on a planar surface of the thick film as well as slopes, topportions, and bottom portions of the channels; connecting the wiringfilm to a conductive portion of the via; forming magneto-sensitiveelements on the slopes of the channels; and connecting the wiring filmto the magneto-sensitive elements.
 16. The manufacturing method for amagnetic sensor according to claim 15, wherein the magnetic sensor iscomposed of a giant magnetoresistive element.
 17. The manufacturingmethod for a magnetic sensor according to claim 15, further comprisingperforming heat treatment on the resist film, thus making terminalsurfaces thereof incline.
 18. The manufacturing method for a magneticsensor according to claim 15, wherein the etching is performed to reducethe resist film and the thick film at an etching selection ratio of 1:1.19. The manufacturing method for a magnetic sensor according to claim15, further comprising forming an insulating film between the thick filmand the passivation film, wherein the insulating film acts as an etchingstopper during the etching.
 20. The manufacturing method for a magneticsensor according to claim 15, further comprising forming a protectionfilm after completion of the magnetic sensor.
 21. The manufacturingmethod for a magnetic sensor according to claim 20, further comprisingforming a conductive pad on the semiconductor substrate and exposing theconductive pad after formation of the protection film.
 22. Themanufacturing method for a magnetic sensor according to claim 15,wherein each of the slopes of the channels formed by the etching isconstituted of a first slope on an upper side and a second slope on alower side, and wherein an inclination angle of the second slope islarger than an inclination angle of the first slope, and wherein themagneto-sensitive element is formed on the second slope.
 23. Amanufacturing method for a magnetic sensor comprising: forming aconductive pad on a semiconductor substrate; forming a thick film;forming a resist film on the thick film; performing etching on theresist film and the thick film, thus forming a plurality of channels inthe thick film, each of the channels having slopes, top portions, andbottom portions; forming an opening in the thick film to form a viaexposing the conductive pad; forming a wiring film on a planar surfaceof the thick film as well as the slopes, top portions, and bottomportions of the channels; connecting the wiring film to the conductivepad; forming magneto-sensitive elements on the slopes of the channels;and connecting the wiring film to the magneto-sensitive elements.